It is known practice to reduce such electromagnetic interference using passive filters. A number of examples of such passive filters are represented in FIGS. 1 to 3, these filters being placed in the electrical line used to transfer electrical energy between the network and the electrical energy storage unit.
FIG. 1 represents an electromagnetic interference filtering device 100 implementing a conventional LC filter for each electrical conductor of the line linking the electrical network 101, represented here in the form of a voltage source, to the electrical energy storage unit 102, represented here in the form of a current source. The device 100 comprises a coil 103 and a capacitor 104. This LC filter has the drawback of exhibiting a significant resonance at its cutoff frequency.
To correct this phenomenon, other electromagnetic interference filtering devices are known.
FIG. 2 represents such a device 110 in which an additional branch 111 is mounted in parallel to the capacitor 104. The damping of the resonance of the conventional LC filter depends on the choice of the ratio between the capacitance value of the capacitor of the additional branch and the capacitance value of the capacitor 104.
FIG. 3 represents another device 120 in which an additional branch 121 is provided for each electrical conductor of the line, this additional branch 121 being mounted in parallel to the coil 103 of said conductor. Each additional branch 121 comprises, in this example, an additional coil 123 and a resistor 124. The additional coils 123 are coupled magnetically together and with the coils 103. The filter 120 is used to damp the resonance at the cutoff frequency of the LC filter according to the device 100 without this cutoff frequency being shifted.
The devices 110 and 120 require the addition of a certain number of additional components to damp the resonance observed at the cutoff frequency of the LC filter of the device 100, which is costly and can create other drawbacks. For example, in the case of the filter 120, each additional branch 121 mounted in parallel to a coil 103 can generate a stray capacitance, affecting the resonant, behavior of the coil 103 and thus degrading the behavior of the device 120.